Microbial contamination and biofilm formation of medical devices is a major issue associated with medical complications and increased costs. Consequently, there is a growing need for novel strategies and exploitation of nanoscience‐based technologies to reduce the interaction of bacteria and microbes with synthetic surfaces. This article focuses on surfaces that are nanostructured, have functional coatings, and generate or release antimicrobial compounds, including “smart surfaces” producing antibiotics on demand. Key requirements for successful antimicrobial surfaces including biocompatibility, mechanical stability, durability, and efficiency are discussed and illustrated with examples of the recent literature. Various nanoscience‐based technologies are described along with new concepts, their advantages, and remaining open questions. Although at an early stage of research, nanoscience‐based strategies for creating antimicrobial surfaces have the advantage of acting at the molecular level, potentially making them more efficient under specific conditions. Moreover, the interface can be fine tuned and specific interactions that depend on the location of the device can be addressed. Finally, remaining important challenges are identified: improvement of the efficacy for long‐term use, extension of the application range to a large spectrum of bacteria, standardized evaluation assays, and combination of passive and active approaches in a single surface to produce multifunctional surfaces.
Biomimetic polymer nanocompartments (polymersomes) with preserved architecture and ion-selective membrane permeability represent cutting-edge mimics of cellular compartmentalization. Here it is studied whether the membrane thickness affects the functionality of ionophores in respect to the transport of Ca ions in synthetic membranes of polymersomes, which are up to 2.6 times thicker than lipid membranes (5 nm). Selective permeability toward calcium ions is achieved by proper insertion of ionomycin, and demonstrated by using specific fluorescence markers encapsulated in their inner cavities. Preservation of polymersome architecture is shown by a combination of light scattering, transmission electron microscopy, and fluorescence spectroscopy. By using a combination of stopped-flow and fluorescence spectroscopy, it is shown that ionomycin can function and transport calcium ions across polymer membranes with thicknesses in the range 10.7-13.4 nm (7.1-8.9 times larger than the size of the ionophore). Thicker membranes induce a decrease in transport, but do not block it due to the intrinsic flexibility of these synthetic membranes. The design of ion selective biomimetic nanocompartments represents a new path toward the development of cellular ion nanosensors and nano-reactors, in which calcium sensitive biomacromolecules can be triggered for specific biological functions.
Co-immobilization of functional, nano-sized assemblies broadens the possibility to engineer dually functionalized active surfaces with nanostructured texture. Surfaces decorated with different nano-assemblies, such as micelles, polymersomes or nanoparticles are in high demand for various applications ranging from catalysis, biosensing up to antimicrobial surfaces. Here, we present a combination of bio-orthogonal and catalyst free strain promoted Azide-Alkyne click (SPAAC) and the thiol-ene reactions to simultaneously co-immobilize various nano-assemblies; we selected polymersome -polymersome and polymersome -micelle assemblies. For the first time, the immobilization method using SPAAC reaction was studied in detail to attach soft, polymeric assemblies on a solid support. Together, the SPAAC, and thiol-ene reactions successfully co-immobilized two unique self-assembled structures on the surfaces. Additionally, polydimethylsiloxane (PDMS) based polymersomes were used as "ink" for direct immobilization from a PDMS based micro stamp onto a surface creating locally defined patterns. Combining immobilization reactions has the advantage to attach any kind of nano-assembly pairs, resulting in surfaces with "desired" interfacial properties. Different nano-assemblies which encapsulate multiple active compounds co-immobilized on a surface will pave the way for the development of multifunctional surfaces with controlled properties and efficiency.
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